So-called heat-shielding performance, based on the reflection or absorption of infrared radiation, can be assessed by determining the solar heat gain coefficient specified by JIS R 3106 or the solar total transmittance (TTS) specified by ISO13837. The lower the TTS, the higher the heat-shielding performance, so that the air-conditioning load can be reduced. A reduction in TTS can be achieved by arranging a reflecting or absorbing component at the positions of entry of the solar radiation, so as to deal with the sunlight spectrum range from ultraviolet to infrared, but lowering transmittance in the visible light region normally brings about a reduction in window visibility. Furthermore, in the case of the front window glass (the windscreen) of an automobile, there is a regulation that the visible light transmittance should be at least 70%, so it is difficult to lower TTS by controlling the transmittance of visible light. Hence, in order to lower TTS in the case of an automobile windscreen, the problem to be addressed is how to efficiently reduce transmittance in the infrared spectrum region in some way, by reflection or absorption.
To tackle with this problem, in Patent Document 1 there is disclosed a thermally-insulating sheet formed by laminating a plurality of layers, specifically at least 6 layers, where said layers are formed by fixing a cholesteric liquid crystal phase wherein the helical pitch has been controlled so as to be consistent with a wavelength in the range 751-2000 nm. In accordance therewith, by laminating a plurality of fixed cholesteric liquid crystal layers of different reflective wavelengths, it is possible to lower the transmittance over the infrared spectrum region (780-1700 nm).